What are the earliest expressions of cognition in infancy? What are the origins, causes, and mechanisms by which individual differences in cognitive competence arise? And, what predictive value has cognitive stature in infancy for cognitive competence in childhood. The research program proposed here seeks to identify origins, early expressions, and implications of cognitive competence in infancy through analyses of infant, mother, and the ways these two principals transact over the child's first four years of life. This research program is driven both by cognitive theory (related to the central importance of mental representation) and by developmental theory (related to transactions of infant and caregiver). A small cohort of infants will be followed longitudinally. In the laboratory, detection, discrimination, and recognition abilities will be assessed at two months and habituation, recognition memory, and cross-modal transfer at six months as they give evidence of mental representation and as they predict the growth of categorization, language, play, and intelligence between one and four years. These cognitive data will be supplemented at each assessment period with observations of infant temperament and with descriptive coding and microanalysis of mother-infant interaction. Thus, the research embraces infant and parent to trace longitudinally transactional patterns between the two, and it is designed to assess infant and mother at multiple points to permit causal analyses of development. Further, the research focuses on patterns of change in individual infants and mother-infant dyads as well as on age-group trends. This research program promises to illuminate basic patterns and processes of normal cognitive development. Moreover, the accomplishment of this research looks forward to the design, construction, and implementation of cognitive enhancement programs for normal infants as well as intervention and remediation programs for infants who have been born at risk biologically, cognitively, or socially for developmental delay.